The Father of Televison

What was the showcased at the 1939 World's Fair in regards to television and by whom was it shown? The 1st presidential speech on television and it was shown to RCA's David Sarnoff

Between 1945 to 1948 the number of commercial (as opposed to experimental) television stations grew from 9 to 48 and the number of cites having commercial service went from 500%. By 1960 there where 440 commercial VHF stations , 75 UHF stations , and 85% of U.S household had a television set.